Police are searching for an armed robber that struck four times this month on the Northwest Side.

In each incident, the suspect walked up to a victim, pulled out a handgun and demanded property, according to an alert from Chicago Police.

The robberies happened:

• about 12:05 a.m. Sept. 1 in the 4300 block of North Sawyer Avenue;
• about 2:30 a.m. Sept. 1 in the 5900 block of North Kimball;
• about 1 a.m. Sept. 3 in the 6200 block of North Kimball; and
• about 1:45 a.m. Monday in the 5000 block of North Drake.

The robber was described as a male, thought to be between 14 and 30 years old, standing between 5-foot-7 and 6-foot-2 and weighing between 140 and 210 pounds, police said.